机械涂覆法制备高光催化活性二氧化钛/金属复合涂层过程解析及光催化活性改善机理研究

In various photocatalysts, TiO2 (titanium dioxide), as its many excellent properties, has been widely used in a number of fields including environment purification. For its recycling, TiO2 is immobilized as films or coatings on substrates by CVD (chemical vapor deposition) and some other methods around the world. However, some problems including low preparation efficiency and high cost hindered these preparation techniques. As the proposal and application of mechanical coating technique, the above problem is expected to be solved thoroughly. In the present project, mechanical coating technique is innovatively used to prepare TiO2/metal composite coatings with high photocatalytic activity on the substrate of ceramic balls. Formation process and formation mechanism of composite coatings are innovatively studied by high-speed photography, molecular dynamics and discrete element simulation. On this basis, the physical model and mathematical model of composite coatings’ formation proess during mechanical coating is attempted to be established. The adhesive strength between spherical ceramic substrate and composite coatings is determined by experimental measurement and simulation calculation. In addition, the adhesion mechanism of composite coatings on ceramic balls is also discussed in depth. The influence of some parameters including grain size and surface morphology of TiO2 on the photocatalytic activity of the composite coatings is examined and the influence mechanism is also investigated. Furthermore, the electron transfer from TiO2 layer towards metal layer is accurately monitored and the relationship between electron transfer and photocatalytic activity is preliminarily quantized. The present project is a matter of great significance for the establishment of complete theory of mechanical coating technique and the elaboration of photocatalysis mechanism of TiO2/metal composite coatings. Mechanical coating technique is expected to become a pratical technique to prepare photocatalyst coatings and therefore promotes the pratical application of photocatalysis.

众多光催化剂中，二氧化钛因其许多优良特性在环境净化等领域得到广泛应用。为便于回收再利用，一般利用化学气相沉积法等方法将二氧化钛以薄膜或涂层形态固定在基体上，但大多数方法的制备效率低且成本较高。随着机械涂覆法的提出及应用，该问题有望得到彻底解决。本项目创新性地采用机械涂覆法以陶瓷球为基体制备高光催化活性二氧化钛/金属复合涂层，利用高速摄像技术及分子动力学和离散元模拟相结合的手段研究复合涂层的形成过程及机理，建立复合涂层形成过程的物理及数学模型；实验测定并计算模拟求解涂层与陶瓷基体的结合强度，深入探究金属粉末在陶瓷球表面的附着机理；系统研究二氧化钛晶粒尺寸和表面形貌等因素对光催化活性的影响及机理，精密监测二氧化钛向金属的电子迁移并量化电子迁移与光催化活性的关系。该项目的研究对完善机械涂覆理论及阐述光催化机理有重要意义,机械涂覆法有望发展成一项实用的光催化涂层制备技术进而推动光催化技术的应用。

为尽快实现光催化技术及制品的实际应用，利用各种手段，例如：化学气相沉积法等，将光催化剂固定在某种基体表面形成连续涂层或者薄膜成为人们的最主要的选择之一。本研究项目创新性地利用机械涂覆技术在陶瓷及金属等基体表面制备了高性能的二氧化钛/金属复合涂层，对前驱体金属涂层的形成过程进行了详细深入的解析，尝试建立起机械涂覆工艺参数-复合涂层微观结构-复合涂层光催化活性三者之间的定性关系，通过各种改善手段提高二氧化钛/金属复合光催化涂层的光催化性能并阐述改善机理。实验结果表明，钛粉末颗粒可以在10小时内在Al2O3或者钢球表面成膜，涂层的厚度与球磨机转速及球磨持续时间紧密相关。利用机械涂覆法及后续热处理制备了TiO2/SnO2复合光催化涂层，研究了后续热处理温度对复合涂层表面形貌的影响，利用熔盐法在TiO2涂层中引入K离子掺杂，K+掺杂的TiO2涂层不仅具有很高的紫外光活性，还具备了一定的可见光活性，而在大肠杆菌灭活实验中也表现出了很高的杀菌性能，这也为光催化涂层在医院及学校等公共场所的应用提供了理论基础。此外，我们更利用TiC0.7N0.3无机粉末制备了C和N共掺杂的TiO2涂层，实验结果表明：该涂层具有全光谱的相应特性，这是开创了利用MXenes逆向将C和N原子从晶格中抽出制备TiO2的先河，为高性能的光催化剂的开发提供了另一种可能方式。此外，我们还研究了晶体缺陷，包括Ti3+和氧空位对TiO2光催化性能的影响，结果表明：适当的表面缺陷和体相缺陷比率对于改善光催化性能是有益的，这与之前有些研究结果是不相同的。作为机械涂覆技术的发展与拓展，我们还制备了Bi2O3涂层，该涂层在模拟太阳光照射下可以在3小时内将孔雀石绿降解矿化，表现出良好的应用前景。在项目实施期内，共发表SCI收录高水平论文9篇，申请国家发明专利1项，参加国际学术会议并发表1次。较为圆满的完成了预期研究目标，取得了较多的研究成果。